Walk through almost any store and you will see prices such as $4.99 or $19.99 far more often than $5.00 or $20.00. Sellers have used prices ending in nine for many years, and researchers have long asked whether the missing cent really changes how shoppers think.
A study published in 2005 by the marketing researchers Manoj Thomas and Vicki Morwitz offered a precise answer. They argued that people read numbers from left to right and form a quick impression of size from the first digit, often before they have finished reading. As a result, $2.99 feels closer to two dollars than to three, even though the difference is only one cent.
Their experiments also showed an important limit. The effect appeared only when the leftmost digit changed. So $2.99 seems noticeably cheaper than $3.00, but $2.59 would not seem cheaper than $2.60, because both prices begin with the same digit. In other words, the nine itself is not what matters. What matters is whether the price stays just below a round number that would change the first digit a shopper sees.
This helps explain why stores choose some prices with great care while leaving others alone.
What is the passage mainly about?